I need some help! I have just resently lowered the rear of my 2001 SC 4x2. I now have a slight vibration at 20 mph and I also have a slight irritaing hum . I thought at one time that it might be the way the truck breaks through the wind but now I don't believe that thought. It sounds like it might a vibration that once going so fast turns into a hum . I have also thought about putting on the old shackles, because I never noticed the hum and vibration before that. I thought I would ask here first before I going to the trouble of changing everything out.
Any help or opinions will be appreciated.
Thanks
Patrick
2001 F150 SC
FIPK

 

Had same problem on my previous vehicle (2002 Supercab). Shims were no help. Going back to the stock shackles resolved the problem. Shame, because it looked much better when lowered 2 inches in the rear.

 

Quite a few folks have posted here about the same problem. I don't recall anyone saying that after they installed the pinion shims the problem remained ?? (Except for tlezcano).

For the few bucks they cost, I'd try it before I went back to the original shackles. I believe I have read that most folks used the 2 degree shims for the 2" rear drop.

Good luck !!

 

Thanks for the help. I have resently search the problem on the forum and found a lot of interesting things.
Again thanks for the reply's.
Patrick